WO2012107306A1 - Procédé d'augmentation de la qualité de signaux reçus par au moins l'un parmi une pluralité de dispositifs destinataires - Google Patents

Procédé d'augmentation de la qualité de signaux reçus par au moins l'un parmi une pluralité de dispositifs destinataires Download PDF

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Publication number
WO2012107306A1
WO2012107306A1 PCT/EP2012/051412 EP2012051412W WO2012107306A1 WO 2012107306 A1 WO2012107306 A1 WO 2012107306A1 EP 2012051412 W EP2012051412 W EP 2012051412W WO 2012107306 A1 WO2012107306 A1 WO 2012107306A1
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WIPO (PCT)
Prior art keywords
modulation symbols
complex modulation
destination
relay device
coding
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PCT/EP2012/051412
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English (en)
Inventor
Mélanie Plainchault
Nicolas Gresset
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Mitsubishi Electric R&D Centre Europe B.V.
Mitsubishi Electric Corporation
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Application filed by Mitsubishi Electric R&D Centre Europe B.V., Mitsubishi Electric Corporation filed Critical Mitsubishi Electric R&D Centre Europe B.V.
Priority to CN201280008400.6A priority Critical patent/CN103416006B/zh
Priority to JP2013552901A priority patent/JP5990199B2/ja
Priority to US13/983,943 priority patent/US9225408B2/en
Publication of WO2012107306A1 publication Critical patent/WO2012107306A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/0413—MIMO systems
    • H04B7/0456—Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting
    • H04B7/046—Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting taking physical layer constraints into account
    • H04B7/0465—Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting taking physical layer constraints into account taking power constraints at power amplifier or emission constraints, e.g. constant modulus, into account
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/022—Site diversity; Macro-diversity
    • H04B7/024—Co-operative use of antennas of several sites, e.g. in co-ordinated multipoint or co-operative multiple-input multiple-output [MIMO] systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/022—Site diversity; Macro-diversity
    • H04B7/026—Co-operative diversity, e.g. using fixed or mobile stations as relays
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/0413—MIMO systems
    • H04B7/0452—Multi-user MIMO systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
    • H04B7/0613—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
    • H04B7/0615—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal
    • H04B7/0617—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal for beam forming

Definitions

  • the present invention generally relates to a method and a device for increasing the quality of signals respectively received by plural destination devices of a wireless telecommunications network, the signals being subject to interference being generated by plural flows of complex modulation symbols transmitted on the same resource.
  • SINR Signal-to-Interference-plus-Noise Ratio
  • the present invention concerns a method for determining a configuration of a wireless telecommunications network, the configuration aiming at increasing a quality of signals received by at least one destination device among plural destination devices of the wireless telecommunications network, plural flows of complex modulation symbols being transmitted on a same resource by respective source devices of the wireless telecommunications network, the source devices being associated with respective destination devices, each source device transmitting at least one flow of complex modulation symbols on said same resource to its associated destination device.
  • the method is such that it comprises the following steps:
  • determining step of determining a pre-coding matrix aiming at being used by the relay device for applying the pre-coding to be able to transmit pre-coded complex modulation symbols, on the same resource as the complex modulation symbols transmitted by the source devices, in order to increase the quality of signals received by at least one destination device,
  • the pre-coding matrix being determined on the basis of the first and second sets of channel matrices, of the selected at least one flow of complex modulation symbols and of a transmission power constraint applicable to the relay device.
  • the configuration takes practically into account hardware power transmission constraints of the relay device that is introduced in the wireless telecommunications network in order to increase the quality of signals received by the at least one destination device.
  • the selecting step comprises a step of obtaining, from each destination device, an information indicating at least one flow of complex modulation symbols aimed at being received by said destination device and for which said destination device is able to decode complex modulation symbols.
  • the distribution of the transmission power of the relay device is focused on the signals that are not yet decoded by the destination devices.
  • the selecting step comprises a step of identifying at least one flow of complex modulation symbols for which the relay device is able to decode complex modulation symbols.
  • the relay device may be incorporated in the wireless telecommunications system in order to increase the quality of signals received by at least one destination device without requiring adaptation of the source devices. Off-the-shelf source devices can therefore be used.
  • the transmission power constraint is related to a global transmission power budget for a whole set of transmit antennas of the relay device or to individual transmission power budget for each transmit antenna of the relay device.
  • the transmission power budget of the relay device is optimally used for cases where the maximal transmission power per device allowed by the specifications of the wireless telecommunications network is more limiting than the transmission power capability of the transmit antennas of the relay device.
  • the transmission power budget of the relay device is optimally used for cases where the transmission power capability of each antenna of the relay device is more limiting than the maximal transmission power per device allowed by the specifications of the wireless telecommunications network.
  • the determining step consists in determining the pre-coding matrix corresponding to an extreme of a function depending on interference observed on at least one flow of complex modulation symbols selected in the selecting step, the interference being observed by the destination device to which the flow of complex modulation symbols is transmitted and said function being subject to a constraint corresponding to the transmission power constraint.
  • the pre-coding matrix can be obtained via computation in analytical form or in numerical form, and is determined to optimize the system performance.
  • said function represents interference between signals received by said at least one destination device, which remains after application, by said at least one destination device, of a minimum mean square error filtering and the determined pre-coding matrix corresponds to a minima of said function.
  • said function represents a maximum interference between signals received by any destination device to which at least one selected flow of complex modulation symbols is transmitted; or a sum of interferences between signals received by the destination devices to which at least one selected flow of complex modulation symbols is transmitted; or a generalized mean of interferences between signals received by all destination devices to which at least one selected flow of complex modulation symbols is transmitted.
  • the pre-coding when said function represents a maximum interference, the pre-coding focuses on the worst interference situation among the destination devices and improves the signal quality for the concerned destination device.
  • the overall performance of the wireless telecommunications system is improved each time for the current worst interference situation.
  • This feature is particularly advantageous when the remaining level of interference plus noise after minimum mean square error filtering is not homogeneous among the destination devices.
  • said function represents a sum of interferences, the improvement of signal quality is beneficial for all the concerned destination devices. This feature is particularly advantageous when the remaining level of interference plus noise after minimum mean square error filtering is substantially homogeneous among the destination devices.
  • the improvement is equally distributed on all destination devices to which at least one selected flow of complex modulation symbols is transmitted.
  • this feature is particularly advantageous to provide a weighted improvement to all these destination devices, in order to provide more improvement to the destination devices observing more interference than others and to reach fairness, i n term s of performance, between the destination devices.
  • said function represents a capacity of the transmission channel between at least one source device and its respective associated destination device and the determined pre-coding matrix corresponds to a maxima of said function.
  • said function represents the minimum transmission channel capacity between any source device transmitting at least one selected flow of complex modulation symbols and its associated destination device; or a sum of transmission channel capacities between the source devices transmitting at least one selected flow of complex modulation symbols and their associated destination device; or a generalized mean of transmission channel capacities between the source devices transmitting at least one selected flow of complex modulation symbols and their associated destination devices.
  • the pre-coding when said function represents a minimum transmission channel capacity, the pre-coding focuses on the worst transmission channel situation among the destination devices and improves the signal quality for the concerned destination device.
  • the overall performance of the wireless telecommunications system is improved each time for the current worst transmission channel situation.
  • This feature is particularly advantageous when the transmission channel capacities are not homogeneous among the destination devices.
  • the function represents a sum of transmission channel capacities, the improvement of signal quality is beneficial for all the concerned destination devices.
  • the transmission channel capacities are substantially homogeneous among the destination devices.
  • said function represents generalized mean of transmission channel capacities, the improvement is equally distributed on all destination devices to which at least one selected flow of complex modulation symbols is transmitted.
  • this feature is particularly advantageous to provide a weighted improvement to all these destination devices, in order to provide more improvement to the destination devices observing a lower capacity than others and to reach fairness, in terms of performance, between the destination devices.
  • the determining step consists in:
  • the determining of the pre-coding matrix is accurate.
  • the feedback of the pre-coding is reduced when said pre-coding matrices are not computed by the relay device.
  • the present invention also concerns a method for increasing a quality of signals received by at least one destination device among plural destination devices of the wireless telecommunications network, plural flows of complex modulation symbols being transmitted on a same resource by respective source devices of the wireless telecommunications network, the source devices being associated with respective destination devices, each source device transmitting at least one flow of complex modulation symbols on said same resource to its associated destination device.
  • the method is such that a relay device of the wireless telecommunications network performs the following steps:
  • determining step of determining a pre-coding matrix aiming at increasing the quality of signals received by at least one destination device, the pre-coding matrix being determined on the basis of the first and second sets of channel matrices, of the selected at least one flow of complex modulation symbols and of a transmission power constraint applicable to the relay device;
  • the quality of signals received by at least one destination device is increased.
  • the configuration takes practically into account the hardware power transmission constraints of the relay device that is introduced in the wireless telecommunications network in order to increase the quality of signals received by the at least one destination device.
  • the selecting step comprises a step of obtaining, from each destination device, an information indicating at least one flow of complex modulation symbols aimed at being received by said destination device and for which said destination device is able, or not, to successfully decode complex modulation symbols
  • the pre-coding step consists in applying the pre-coding to at least one complex modulation symbols generated by the relay device following a decoding of complex modulation symbols received from at least one respective source device, or in applying the pre-coding to an estimate of at least one complex modulation symbol received from at least one respective source device.
  • the improvement then focuses on flows of complex modulation symbols for which there is an effective need, as indicated by the destination devices.
  • the pre-coding to at least one complex modulation symbols generated by the relay device following a decoding of received complex modulation symbols
  • the increase of the signal quality at the concerned destination devices is yet improved.
  • a trade-off may be found between improvement of the signal quality at the concerned destination devices and the design complexity of the relay device, as well as the processing latency of the relay device.
  • the selecting step comprises a step of identifying at least one flow of complex modulation symbols for which the relay device is able to decode complex modulation symbols, and the pre-coding step consists in applying the pre-coding to said complex modulation symbols that the relay device is able to decode.
  • the relay device may be incorporated in the wireless telecommunications system in order to increase the quality of signals received by at least one destination device with limited adaptation of the destination devices.
  • the present invention also concerns a device for determining a configuration of a wireless telecommunications network, the configuration aiming at increasing a quality of signals received by at least one destination device among plural destination devices of the wireless telecommunications network, plural flows of complex modulation symbols being transmitted on a same resource by respective source devices of the wireless telecommunications network, the source devices being associated with respective destination devices, each source device transmitting at least one flow of complex modulation symbols on said same resource to its associated destination device.
  • the device is such that it comprises the following means:
  • - obtaining means for obtaining a first set of channel matrices representing transmission channels between the source devices and each destination device and a second set of channel matrices representing transmission channels between a relay device of the wireless telecommunications network and each destination device;
  • - selecting means for selecting at least one flow of complex modulation symbols for which the relay device has to apply a pre-coding
  • - determining means for determining a pre-coding matrix aiming at being used by the relay device for applying the pre-coding to be able to transmit pre-coded complex modulation symbols, on the same resource as the complex modulation symbols transmitted by the source devices, in order to increase the quality of signals received by at least one destination device,
  • the determining means being adapted so that the pre-coding matrix is determined on the basis of the first and second sets of channel matrices, of the selected at least one flow of complex modulation symbols and of a transmission power constraint applicable to the relay device.
  • the present invention also concerns a relay device for increasing a quality of signals received by at least one destination device among plural destination devices of the wireless telecommunications network, plural flows of complex modulation symbols being transmitted on a same resource by respective source devices of the wireless telecommunications network, the source devices being associated with respective destination devices, each source device transmitting at least one flow of complex modulation symbols on said same resource to its associated destination device.
  • the relay device is such that it comprises the following means:
  • - obtaining means for obtaining a first set of channel matrices representing transmission channels between the source devices and each destination device and a second set of channel matrices representing transmission channels between the relay device and each destination device;
  • - selecting means for selecting at least one flow of complex modulation symbols for which the relay device has to apply a pre-coding
  • - determining means for determining a pre-coding matrix aiming at increasing the quality of signals received by at least one destination device, the pre-coding matrix being determined on the basis of the first and second sets of channel matrices, of the selected at least one flow of complex modulation symbols and of a transmission power constraint applicable to the relay device;
  • - pre-coding means for applying the pre-coding to the selected at least flow of complex modulation symbols, by using the determined pre-coding matrix in order to generate pre-coded complex modulation symbols
  • the present invention also concerns, in at least one embodiment, a computer program that can be downloaded from a communication network and/or stored on a medium that can be read by a computer and run by a processor.
  • This computer program comprises instructions for implementing the aforementioned methods in any one of their various embodiments, when said program is run by the processor.
  • the present invention also concerns an information storage means, storing a computer program comprising a set of instructions that can be run by a processor for implementing the aforementioned methods in any one of their various embodiments, when the stored information is read by a computer and run by a processor.
  • Fig. 1 schematically represents an architecture of a wireless telecommunications network in which the present invention may be implemented
  • Fig. 2 schematically represents an architecture of a relay device of the telecommunications network of Fig. 1;
  • Fig. 3 schematically represents an algorithm for determining a pre-coding matrix to be used by the relay device in order to generate pre-coded complex modulation symbols
  • Fig. 4 schematically represents an algorithm performed by the relay device for transmitting pre-coded complex modulation symbols to at least one destination device of the telecommunications network of Fig. 1, according to a first embodiment
  • Fig. 5 schematically represents an algorithm performed by the relay device for transmitting pre-coded complex modulation symbols to at least one destination device of the telecommunications network of Fig. 1, according to a second embodiment.
  • Fig. 1 schematically represents an architecture of a wireless telecommunications network in which the present invention may be implemented.
  • the wireless telecommunications network 100 may be a local area network or a wireless cellular telecommunications network.
  • plural source devices 101, 102, 103, 104 respectively transmit information words in the form of signals to plural destination devices 1 1 1, 1 12, 1 13, 1 14 using a same frequency and time resource.
  • the plurality of source devices 101, 102, 103 and 104 transmit signals that overlap in terms of transmission frequency or frequencies and that further overlap in terms of transmission time period or periods.
  • the source device 101 transmits at least one flow of complex modulation symbols to the destination device 1 1
  • the source device 102 transmits at least one flow of complex modulation symbols to the destination device 1
  • the source device 103 transmits at least one flow of complex modulation symbols to the destination device 1 13
  • the source device 104 transmits at least one flow of complex modulation symbols to the destination device 1 14.
  • the source devices 101, 102, 103, 104 and the destination devices 1 1 1, 1 12, 1 13, 1 14 are associated.
  • the wireless telecommunications network 100 therefore also comprises the same number S of destination devices.
  • N the number of flows of complex modulation symbols transmitted from the source devices 101, 102, 103, 104 to the destination devices 1 1 1, 1 12, 1 13, 1 14. It can be noticed that N ⁇ S.
  • the source devices 101, 102, 103, 104 may be mobile terminals and the destination devices 1 1 1, 1 12, 1 13, 1 14 may be base stations, such as in the uplink context of a cellular telecommunications network.
  • the source devices 101, 102, 103, 104 may be base stations and the destination devices 1 1 1, 1 12, 1 13, 1 14 may be mobile terminals, such as in the downlink context of a cellular telecommunications network.
  • Each source device 101, 102, 103, 104 may perform beamforming in order to transmit plural flows of complex modulation symbols to its associated destination devices 1 1 1, 1 12, 1 13, 1 14.
  • Each source device 101 , 102, 103, 104 transmits at least one information word in the form of at least one flow of complex modulation symbols to its associated destination device 1 1 1, 1 12, 1 13, 1 14.
  • the flow, or flows, of complex modulation symbols transmitted by one source device 101, 102, 103 or 104 may produce interference with other flow, or flows, of complex modulation symbols.
  • Each source device 101, 102, 103 and 104 may comprise an encoder that encodes information words, which are further interleaved to produce coded bits. Encoding and interleaving is generally performed by a rate matching algorithm, such as the one used in the 3GPP-LTE ⁇ Third Generation Partnership Project-Long Term Evolution) standard, that allows generating vectors of any size from the information words or, in other words, that provides a wide range of possible coding rates.
  • a rate matching algorithm such as the one used in the 3GPP-LTE ⁇ Third Generation Partnership Project-Long Term Evolution
  • the coded bits are then processed by a discrete modulation component, which may for instance be a QPSK ⁇ Quadrature Phase Shift Keying) modulator or a 16- QAM ⁇ Quadrature Amplitude Modulation) modulator, in order to obtain complex modulation symbols.
  • a discrete modulation component which may for instance be a QPSK ⁇ Quadrature Phase Shift Keying) modulator or a 16- QAM ⁇ Quadrature Amplitude Modulation) modulator, in order to obtain complex modulation symbols.
  • the flows of complex modulation symbols may be generated by using the same modulation scheme or different modulation schemes. Each flow of complex modulation symbols may be generated by successively using different modulation schemes.
  • the source devices 101, 102, 103, 104 may generate the complex modulation symbols without using the aforementioned encoder.
  • the principle of the present invention would also operate in order to increase the quality of the signals received by at least one of the destination devices 111, 112, 113, 114, especially when an MMSE ⁇ Minimum Mean Square Error) filtering module is included in each destination device 111, 112, 113, 114.
  • the information words are provided with redundancy check data, such as a CRC ⁇ Cyclic Redundancy-Check) portion.
  • redundancy check data such as a CRC ⁇ Cyclic Redundancy-Check
  • an HARQ ⁇ Hybrid-ARQ or Hybrid Automatic Repeat reQuest) mechanism is preferably used to provide retransmission capability from the source devices 100, 101,
  • the wireless telecommunications network 100 further comprises a relay device 120.
  • the source devices 101, 102, 103, 104 are not aware of the presence of the relay device 120 in the wireless telecommunications network 100.
  • the source devices 101, 102, 103, 104 don't participate in the pre- coding detailed hereinafter. This pre-coding is therefore exclusively performed by the relay device 120.
  • the relay device 120 is adapted to obtain at least one complex modulation symbol, or estimate thereof, transmitted by at least one respective source device 101, 102, 103 or 104.
  • the complex modulation symbols may be obtained by retrieving information words transmitted by the concerned source devices, and applying appropriate coding scheme, rate matching and modulation processes. It means that the relay device 120 is adapted to apply coding scheme, rate matching and modulation processes similar to those of the concerned source device 101, 102, 103 or 104.
  • Estimates of information word may also be obtained by using a data link from the source devices 101, 102, 103, 104 to the relay device 120, which can be a wireless link or a fixed access link.
  • the relay device 120 is further adapted to apply a pre-coding to the obtained complex modulation symbols by using a pre-coding matrix P.
  • the relay device 120 therefore generates pre-coded complex modulation symbols.
  • the pre-coding matrix P is defined so as to improve the quality of the signals received by at least one destination device 1 1 1, 1 12, 1 13, 1 14.
  • the relay device 120 is further adapted to transmit the pre-coded complex modulation symbols to the concerned destination device(s) 1 1 1, 1 12, 1 13, 1 14. Each concerned destination device 1 1 1, 1 12, 1 13, 1 14 thus receives complex modulation symbols from its associated source device 101, 102, 103 or 104 and from the relay device 120. It has to be further noted that the relay device 120 transmits the pre-coded complex modulation symbols using the same resource as the concerned source device 101, 102, 103 or 104.
  • the relay device 120 receives beforehand the concerned information words or the complex modulation symbols from the concerned source device 101, 102, 103 or 104. For instance, a dedicated communication link between the relay device 120 and the concerned source device 101, 102, 103 or 104 may be set up.
  • the relay device 120 is able to use information words retrieved by applying a decoding to received complex modulation symbols.
  • the relay device 120 is therefore able to generate and transmit pre-coded complex modulation symbols from the retrieved information words.
  • An occurrence of such a retransmission may be determined by capturing and analysing the feedback provided by the concerned destination device 111, 112, 113 or 114, when an HARQ mechanism is used between the source devices 101, 102, 103, 104 and their respective associated destination devices 111, 112, 113, 114.
  • Each destination device 111, 112, 113, 114 preferably comprises an MMSE filtering module to retrieve the complex modulation symbols transmitted by its associated source device 101, 102, 103 or 104. However, after decoding as performed by the MMSE filtering module, interferences may remain.
  • index j an index used to identify each source device among the S source devices of the wireless telecommunications network 100. It can be noticed that the index j also identifies the destination device 111, 112, 113 or 114 associated with the considered source device 101, 102, 103 or 104.
  • ⁇ a set of indexes used to identify each flow of complex modulation symbols transmitted from any source device 101, 102, 103 or 104 to its associated destination device 1 1 1, 1 12, 113 or 1 14.
  • the cardinality of ⁇ is therefore equal to N.
  • ⁇ ; ⁇ the subset of at least one index such that, if an index b of ⁇ belongs to ⁇ ; ⁇ , then the complex modulation symbol X b is transmitted by the source device identified by the index j to its associated destination device. Therefore the subset ⁇ ; ⁇ is used to identify the flow, or flows, of complex modulation symbols transmitted by the source device identified by the index j to its associated destination device.
  • X a vector of complex modulation symbols transmitted by the source devices 101, 102, 103, 104 during a given period of time.
  • Let' s further denote X j the vector of complex modulation symbols transmitted by the source device identified by the index j and which are aimed at being received by the destination device identified by the index j.
  • D j a matrix, which size is N X N, having non-null entries only on the diagonal at the indexes belonging to ⁇ ; ⁇ , said non-null entries being equal to 1. It can be noticed that:
  • ⁇ represents the transpose conjugate of M.
  • the destination device identified by the index j Upon reception of a vector complex of modulation symbols Y j corresponding to the vector of complex modulation symbols X j , the destination device identified by the index j performs an estimation of the vector D j X, and obtains an estimated vector X j of complex modulation symbols.
  • the size of the estimated vector X j is ⁇ and the estimated vector X j comprises zeros at position indexes not in the subset ⁇ ; ⁇ .
  • the estimated vector X j is obtained as follows:
  • W j (P) DJ(HJ + F j PA r y ((H j + F j PA r )D j (H j + F ; PA r ) ⁇ + ⁇ ,- (?))
  • H j is a matrix corresponding to the transmission channel observed between the source devices 101, 102, 103, 104 and the destination device identified by the index j. H j is therefore a channel matrix representing the transmission channel between the source devices 101, 102, 103, 104, and the destination device identified by the index j.
  • the size of H j is R j X N , wherein R j i s the number of receive antennas of the destination device identified by the index j;
  • - r ⁇ j is a vector, which size is R j x 1, representing the additive white Gaussian noise with variance N 0 per real dimension observed at each receive antenna of the destination device identified by the index j, which also encompasses the interference from the neighbouring transmission systems sharing the same resource, typically sharing the same transmission frequency or frequency range;
  • Fj is a matrix corresponding to the transmission channel observed between the relay device 120 and the destination device identified by the index j.
  • Fj is therefore a channel matrix representing the transmission channel between the relay device 120 and the destination device identified by the index j.
  • the size of Fj is Rj x T r , wherein
  • T r is the number of transmit antennas of the relay device 120
  • a r is a diagonal matrix, which size is N X N, with ones at position indexes i on the diagonal corresponding to a selection of flows of complex modulation symbols X t for which the relay device 120 has to apply the pre-coding and with zeros elsewhere;
  • P is the pre-coding matrix, which size is T r X N;
  • ⁇ j (P) is the covariance matrix of the interference observed by the destination device identified by the index j.
  • the channel matrices Hj and Fj are preferably scaled by the transmission power of the source devices 101, 102, 103, 104 and of the relay device 120 respectively, and also take into account the channel wide band attenuation.
  • the pre-coding matrix may be understood as the association of the matrices A r and P, and more particularly as the product PA r .
  • the covariance matrix ⁇ ; -(P) is expressed as follows:
  • ⁇ j (P) (Hj + FjPA r )Dj (Hj + FjPArf + 2ajl R .
  • This situation is also referred to as full CSI (Channel State Information) knowledge at the considered destination device 11 1, 112, 113 or 114.
  • the considered destination device 111, 112, 113 or 114 may then transmit this information to the relay device 120.
  • the covariance matrix ⁇ ; -(P) is expressed as follows:
  • ⁇ j (P) E [(Hj + FjPA r )Dj (Hj + F ; PA r ) ⁇ ] + 2ajl R .
  • E [Z] represents the expectation of Z.
  • This situation is also referred to as partial CSI knowledge at the considered destination device 1 1 1, 1 12, 1 13 or 1 14.
  • the considered destination device 1 1 1, 1 12, 1 13 or 1 14 transmits this information to the relay device 120.
  • the considered destination device 1 1 1, 1 12, 1 13 or 1 14 may transmit only partial CSI knowledge to the relay device 120.
  • Fig. 2 schematically represents an architecture of the relay device 120.
  • the relay device 120 comprises the following components interconnected by a communications bus 210: a processor, microprocessor, microcontroller or CPU (Central Processing Unit) 200; a RAM (Random-Access Memory) 201 ; a ROM (Read-Only Memory) 202; a HDD (Hard-Disk Drive) 203, or any other device adapted to read information stored on storage means; a first wireless communication interface 204 and a second wireless communication interface 205.
  • a processor, microprocessor, microcontroller or CPU Central Processing Unit
  • RAM Random-Access Memory
  • ROM Read-Only Memory
  • HDD Hard-Disk Drive
  • CPU 200 is capable of executing instructions loaded into RAM 201 from ROM 202 or from an external memory, such as HDD 203. After the relay device 120 has been powered on, CPU 200 is capable of reading instructions from RAM 201 and executing these instructions.
  • the instructions form one computer program that causes CPU 200 to perform some or all of the steps of the algorithms described hereafter with regard to Figs. 3, 4 and 5.
  • any and all steps of the algorithms described hereafter with regard to Figs. 3, 4 and 5 may be implemented in software by the execution of a set of instructions or program by a programmable computing machine, such as a PC (Personal Computer), a DSP (Digital Signal Processor) or a microcontroller; or else implemented in hardware by a machine or a dedicated component, such as an FPGA (Field- Programmable Gate Array) or an ASIC (Application-Specific Integrated Circuit).
  • a programmable computing machine such as a PC (Personal Computer), a DSP (Digital Signal Processor) or a microcontroller; or else implemented in hardware by a machine or a dedicated component, such as an FPGA (Field- Programmable Gate Array) or an ASIC (Application-Specific Integrated Circuit).
  • the wireless communication interface 204 enables the relay device 120 to receive signals from the source devices 101, 102, 103, 104.
  • the wireless communication interface 205 enables the relay device 120 to transmit signal s to the destination devices 1 1 1 , 1 12, 1 13 , 1 14.
  • the wireless communication interface 205 may also enable the relay device 120 to receive signals from the destination devices 111, 112, 113, 114.
  • the relay device 120 is not full-duplex, but is half- duplex.
  • a single wireless communication interface is implemented and is alternatively used in reception and transmission mode.
  • destination devices 111, 112, 113, 114 may also be implemented on the basis of the architecture schematically shown in Fig.2.
  • Fig.3 schematically represents an algorithm for determining the pre-coding matrix P , according to at least one embodiment of the present invention.
  • the algorithm of Fig.3 aims at defining a configuration of the wireless telecommunications network 100, namely via setting the pre-coding matrix P, aiming at increasing the quality of signals received by at least one destination device 111, 112, 113, 114.
  • the algorithm of Fig.3 is described hereafter as being performed by the relay device 120.
  • This algorithm may however be performed by a device other than the relay device 120.
  • This other device collects the necessary information from the relay device 120 and the destination devices 111, 112, 113, 114 and provides the pre-coding matrix P or a plurality of pre-coding matrices to the relay device 120, in a same manner as aforementioned.
  • This other device may, or not, be actually part of the wireless telecommunications network 100. For instance, this other device may be connected to the relay device 120 by a wired link.
  • the relay device 120 obtains information about the channels observed between the source devices 101, 102, 103, 104 and the destination devices 111, 112, 113, 114, as well as between the relay device 120 and the destination devices 111, 112, 113, 114. Such information is provided by each destination device 111, 112, 113, 114.
  • the destination devices 111, 112, 113, 114 may obtain this information by short-term measurements performed on the channels. In the state of the art, this information is often referred to as short-term channel state information, and is practically suitable for slow- varying channel conditions.
  • the destination devices 111, 112, 113, 114 may also obtain this information by long-term measurements performed on the channels, such as on the basis of the covariance matrices of the MIMO channels.
  • this information is often referred to as long-term channel state information, and is practically suitable for fast-varying channel conditions, or in systems with limited feedback.
  • An approach for determining the channel state information is based on a training sequence, or pilot sequence, where a known signal is transmitted and the channel matrix representing the transmission channel conditions is estimated using the combined knowledge of the transmitted and received signal.
  • Each destination device identified by the index j may transmit to the relay device 120 the channel matrices Hj and Fj , or l ong-term channel state information to allow the relay device 120 to build them or equivalent matrices.
  • the relay device 120 obtains the channel matrices Hj and Fj, or equivalent matrices, at least for the transmission channels on which flows of complex modulation symbols that can be selected in a step S403 or in a step S502 detailed hereafter with regard to Fig. 4 or 5 respectively.
  • the relay device 120 obtains a first set of channel matrices Hj representing transmission channels between the source devices and each destination device and a second set of channel matrices Fj representing transmission channels between the relay device 120 and each destination device.
  • the relay device obtains a selection of flows of complex modulation symbols for which the relay device 120 has to apply the pre- coding. This selection results from the execution of the step S403 or the step S502 detailed hereafter with regard to Fig. 4 or 5 respectively.
  • the relay device 120 determines the pre-coding matrix P on the basis of the first and second sets of channel matrices, of the selection of at least one flow of complex modulation symbols and of a transmission power constraint applicable to the relay device 120.
  • This transmission power constraint allows determining coefficients of the pre- coding matrix P that meet the requirements of the transmission power specifications or characteristics of the relay device 120 and/or more generally of the wireless telecommunications network 100.
  • Such requirements of the wireless telecommunications network 100 may be defined by governmental regulations.
  • the transmission power constraint is related to a global transmission power budget for the whole set of the T r transmit antennas of the relay device 120.
  • the transmission power budget of the relay device 120 is optimally used for cases where the maximal transmission power per device allowed by the specifications of the wireless telecommunications network 100 is more limiting than the transmission power capability of the transmit antennas of the relay device 120.
  • the transmission power constraint i(P) may be expressed as follows, on the basis of a trace function:
  • h(P) Trace (A r ⁇ P ⁇ PA r ) - T r
  • the transmission power constraint is related to an individual transmission power budget for each transmit antenna of the relay device 120.
  • the transmission power budget of the relay device 120 is optimally used for cases where the transmission power capability of each antenna of the relay device 120 is more limiting than the maximal transmission power per device allowed by the specifications of the wireless telecommunications network 100.
  • the transmission power constraint h(P) may be expressed as follows, on the basis of computing a determinant, assuming that N is larger than T r :
  • I Tr is an identity matrix of size T r .
  • the transmission power constraint h(P) is related to a global transmission power budget for the whole set of the T r transmit antennas of the relay device 120.
  • the relay device 120 determines the pre-coding matrix P that corresponds to an extreme of a function depending on an interference between signals received by the destination devices 1 1 1, 1 12, 1 13, 1 14, said function being subject to a constraint corresponding to the transmission power constraint.
  • said function represents the remaining level of interference plus noise after MMSE filtering by at least one destination device 1 1 1, 1 12, 1 13, 1 14.
  • the pre-coding matrix P then corresponds to a minima of this function.
  • said function represents the channel capacity between at least one source device 101, 102, 103, 104 and the associated at least one destination device 1 1 1, 1 12, 1 13, 114.
  • the pre-coding matrix P then corresponds to a maxima of this function.
  • the relay device 120 determines the pre-coding matrix P so that it reduces the total remaining level of interference plus noise £ tot (P), taking into account the transmission power constraint h(P).
  • the total remaining level of interference plus noise £ tot (P) is understood as the sum of remaining level of interference plus noise at all the destination devices 1 1 1, 1 12, 1 13, 1 14 for which at least one received flow of complex modulation symbols belongs to the selection obtained in step S301.
  • the total remaining level of inte P) is expressed as follows:
  • the relay device 120 determines the pre-coding matrix P corresponding to, in a Lagrange multipliers method, an extreme of a function depending on an interference between signals received by the destination devices, 1 1 1, 1 12, 1 13, 1 14 for which at least one received flow of complex modulation symbols belongs to the selection obtained in step S301, said function being subject to a constraint corresponding to the transmission power constraint.
  • the Lagrange multipliers method applied to the aforementioned expressions of £ tot (P) and h(P) is as foll
  • the relay device 120 therefore determines the pre-coding matrix P that solves this system of equations, wherein ⁇ represents the Lagrange multiplier.
  • the relay device 120 determines the pre-coding matrix P by using an iterative optimization algorithm, such as for instance a gradient descent.
  • the gradient descent method is used to iteratively determine the pre-coding matrix P that corresponds to an extreme of a function depending on interference between signals received by the destination devices 1 1 1, 112, 1 13, 1 14 for which at least one received flow of complex modulation symbols belongs to the selection obtained in step S301, said function being subject to a constraint corresponding to the transmission power constraint.
  • the gradi ent descent method appli ed to the aforementioned expressions of E tot (P) and h ⁇ P) is as follows:
  • P k * is the complex conjugate of P k and ⁇ is a predefined convergence parameter and k represents the index of iteration.
  • the convergence parameter ⁇ may be set to a value obtained by field tests.
  • the initial matrix P 0 may be arbitrarily defined or selected from among a predefined set of pre-coding matrices.
  • the relay device 120 then checks if the resulting matrix P k+1 meets the requirements of the transmission power constraint h(P) . If these requirements are met, the relay device 120 considers that it has found a suitable pre-coding matrix P. Otherwise, another iteration is performed wherein P k+1 becomes P k .
  • P k+1 is projected on the transmission power constraint h(P) as follows, and iterations are performed until convergence of P k+1 and P k+1 :
  • the relay device 120 stores a plurality of pre-coding matrices.
  • the relay device 120 determines what pre-coding matrix from among the plurality corresponds to an extreme of a function depending on an interference between signals received by at least one destination device 1 1 1 , 1 12, 1 13, 1 14 for which at least one received flow of complex modulation symbols belongs to the selection obtained in step S301, said function being subject to a constraint corresponding to the transmission power constraint.
  • the relay device 120 determines, for each matrix of this plurality, the total remaining level of interference plus noise £ tot (P), taking into account the transmission power constraint h(P).
  • the relay device 120 selects, if any, the matrix that minimizes the total remaining level of interference plus noise £ tot (P), while meeting the requirements of the transmission power constraint h(P).
  • the selected matrix then becomes the pre- coding matrix P to be applied by the relay device 120 in order to generate pre-coded complex modulation symbols.
  • the relay device 120 determines the pre-coding matrix P so that it reduces the maximum remaining level of interference plus noise £ max (P among the destination devices 1 1 1, 1 12, 1 13, 1 14 for which at least one received flow of complex modulation symbols belongs to the selection obtained in step S301 , taking into account the transmission power constraint /i(P) .
  • the maximum remaining level of interference plus n follows:
  • the relay device 120 determines the pre-coding matrix P corresponding to, in a Lagrange multipliers method, an extreme of a function depending on an interference between signals received by the destination devices 1 1 1, 1 12, 1 13, 1 14 for which at least one received flow of complex modulation symbols belongs to the selection obtained in step S301, said function being subject to a constraint corresponding to the transmission power constraint.
  • the Lagrange multipliers method applied to the aforementioned expressions of £ max (P and h(P) is as follows:
  • the relay device 120 therefore determines the pre-coding matrix P that solves this system of equations.
  • the relay device 120 determines the pre-coding matrix P by using an iterative optimization algorithm, such as for instance a gradient descent.
  • the gradient descent method is used to iteratively determine the pre-coding matrix P that corresponds to an extreme of a function depending on interference between signals received by the destination devices 1 1 1, 1 12, 1 13, 1 14 for which at least one received flow of complex modulation symbols belongs to the selection obtained in step S301, said function being subject to a constraint corresponding to the transmission power constraint.
  • the gradient descent method applied to the aforementioned expressions of £ max (P and h(P) is as follows:
  • the initial matrix P 0 may be arbitrarily defined or selected from among a predefined set of pre-coding matrices.
  • the relay device 120 then checks if the resulting matrix P k+1 meets the requirements of the transmission power constraint h(P) . If these requirements are met, the relay device 120 considers that it has found a suitable pre-coding matrix P. Otherwise, another iteration is performed wherein P k+1 becomes P k .
  • P k+1 is projected on the transmission power constraint h(P) as follows, and iterations are performed until convergence of P k+1 and P k+1 :
  • the relay device 120 stores a plurality of pre-coding matrices.
  • the relay device 120 determines what pre-coding matrix from among the plurality corresponds to an extreme of a function depending on an interference between signals received by at least one destination device 1 1 1 , 1 12, 1 13, 1 14 for which at least one received flow of complex modulation symbols belongs to the selection obtained in step S301, said function being subject to a constraint corresponding to the transmission power constraint.
  • the relay device 120 determines, for each matrix of this plurality, the maximum remaining level of interference plus noise £ max taking into account the transmission power constraint h(P) .
  • the relay device 120 selects, if any, the matrix that minimizes the maximum remaining level of interference plus noise £ max while meeting the requirements of the transmission power constraint h(P) .
  • the selected matrix then becomes the pre-coding matrix P to be applied by the relay device 120 in order to generate pre-coded complex modulation symbols.
  • a linearization of the maximum remaining level of interference plus noise may be applied.
  • the gradient descent may then be expressed as foll
  • the relay device 120 then checks if the resulting matrix P k+1 meets the requirements of the transmission power constraint /i(P). If these requirements are met, the relay device 120 considers that it has found a suitable pre-coding matrix P. Otherwise, another iteration is performed wherein P k+1 becomes P k .
  • P k+1 is projected on the transmission power constraint h(P) as follows, and iterations are performed until convergence of P k+1 and P k+1 :
  • the relay device 120 determines the pre-coding matrix P so that it reduces the generalized mean with exponent v of the remaining level of interference £ gm (P among the destination devices 111, 112, 113, 114 for which at least one received flow of complex modulation symbols belongs to the selection obtained in step S301, taking into account the transmission power constraint h(P) .
  • the generalized mean with exponent v of the remaining level of interference £ register m (P) is expressed as follows:
  • the exponent v is chosen equal to 1, the sum of the remaining levels of interference plus noise observed at all the destination devices 111, 112, 113, 114 is maximized. If the exponent v is chosen as a high positive value, the largest remaining level of interference plus noise will be minimized in priority.
  • the relay device 120 determines the pre-coding matrix P corresponding to, in a Lagrange multipliers method, an extreme of a function depending on an interference between signals received by the destination devices 111, 112, 113, 114 for which at least one received flow of complex modulation symbols belongs to the selection obtained in step S301, said function being subject to a constraint corresponding to the transmission power constraint.
  • the Lagrange multipliers method applied to the aforementioned expressions of £ 5m (P) and h(P) is as follows:
  • the relay device 120 therefore determines the pre-coding matrix P that solves this system of equations.
  • the relay device 120 determines the pre-coding matrix P by using an iterative optimization algorithm, such as for instance a gradient descent.
  • the gradient descent method is used to iteratively determine the pre-coding matrix P that corresponds to an extreme of a function depending on interference between signals received by the destination devices 111, 112, 113, 114 for which at least one received flow of complex modulation symbols belongs to the selection obtained in step S301, said function being subject to a constraint corresponding to the transmission power constraint.
  • the gradient descent method applied to the aforementioned expressions of £ submit m (P) and h(P) is as follows:
  • the initial matrix P 0 may be arbitrarily defined or selected from among a predefined set of pre-coding matrices.
  • the relay device 120 then checks if the resulting matrix P k+1 meets the requirements of the transmission power constraint h(P) . If these requirements are met, the relay device 120 considers that it has found a suitable pre-coding matrix P. Otherwise, another iteration is performed wherein P k+1 becomes P k .
  • P k+1 is projected on the transmission power constraint h(P) as follows, and iterations are performed until convergence of P k+1 and P k+1 :
  • the relay device 120 stores a plurality of pre-coding matrices.
  • the relay device 120 determines what pre-coding matrix from among the plurality corresponds to an extreme of a function depending on an interference between signals received by at least one destination device 111, 112, 113, 114 for which at least one received flow of complex modulation symbols belongs to the selection obtained in step S301, said function being subject to a constraint corresponding to the transmission power constraint.
  • the relay device 120 determines, for each matrix of this plurality, the maximum remaining level of interference £ gm (P) , taking into account the transmission power constraint h(P) .
  • the relay device 120 selects, if any, the matrix that minimizes the maximum remaining level of interference £ gm (P) , while meeting the requirements of the transmission power constraint h(P) .
  • the selected matrix then becomes the pre-coding matrix P to be applied by the relay device 120 in order to generate pre-coded complex modulation symbols.
  • ⁇ ,-( ⁇ ) Trace ⁇ 2N 0 Dj ((H,- + F ; PA r ) ⁇ (H ; + FjPA r ) + 2 ⁇ ; 2 / spirit)
  • the matrix A j represents an estimation of the useful channel for processing a joint decoding of the complex modulation symbols by the destination device identified by the index j
  • the matrix B j represents interference statistics observed at the destination device identified by the index j.
  • the destination device identified by the index j then provides the matrices A j and B j to the relay device 120.
  • the pre-coding matrix P can be used in order to increase the quality of the signals received by at least one destination device 1 1 1, 1 12, 1 13, 1 14 upstream from the MMSE filtering module or even when the destination devices 1 1 1, 1 12, 1 13, 1 14 don't include an MMSE filtering module.
  • the relay device 120 may determine the pre-coding matrix P that corresponds to an extreme of a function representing the capacity of the transmission channel s between the source devices 101 , 102, 103 , 104, and their associated destination devices 1 1 1, 1 12, 1 13, 1 14, for which at least one transmitted flow of complex modulation symbols belongs to the selection obtained in step S301.
  • the pre- coding matrix P corresponds in this case to a maxima of such function, or equivalently to a minima of the additive inverse function.
  • the capacity C ; - (P) of the transmi ssion channel from one source device identified by the index j to its associated destination device may be expressed as follows:
  • the relay device 120 may determine the pre-coding matrix P that maximizes, taking into account the transmission power constraint h(P), the generalized mean with exponent v of the channel capacity of the wireless telecommunications network 100, referring to the transmission channels from the source devices 101, 102, 103, 104 to their respective associated destination devices 1 1 1, 1 12, 1 13, 1 14, and for which at least one transmitted flow of complex modulation symbols belongs to the selection obtained in step S301.
  • the relay device 120 targets determining the pre- coding matrix P that corresponds, taking into account the transmission power constraint h(P), to an extreme of the generalized mean of the transmission channel capacities from the source devices 101 , 102, 103, 104 to their respective associated destination devices 1 1 1, 1 12, 1 13, 1 14, and for which at least one transmitted flow of complex modulation symbols belongs to the selection obtained in step S301.
  • the transmission channel capacity C(P) to be maximized is then expressed as follows:
  • the relay device 120 determines the pre-coding matrix P corresponding to, in a Lagrange multipliers method, an extreme of a function depending on an interference between signals received by the destination devices 1 1 1, 1 12, 1 13, 1 14 for which at least one received flow of complex modulation symbols belongs to the selection obtained in step S301, said function being subject to a constraint corresponding to the transmission power constraint.
  • the Lagrange multipliers method applied to the aforementioned expressions of C(P) and
  • exponent v is chosen equal to 1 , the sum of all capacities is maximized. If exponent v is chosen as a negative value, the lowest capacities of the transmission channels from the source devices 101, 102, 103, 104 to their respective associated destination devices 111, 112, 113, 114, and for which at least one received flow of complex modulation symbols belongs to the selection obtained in step S301, will be maximized in priority.
  • the relay device 120 may determine the pre-coding matrix P by using an iterative optimization algorithm, such as for instance a gradient descent.
  • the gradient descent method is used to iteratively determine the pre-coding matrix P that corresponds to an extreme of a function depending on the capacity of the transmission channels from the source devices 101, 102, 103, 104 and their respective associated destination devices 1 1 1, 1 12, 113, 1 14, said function being subject to a constraint corresponding to the transmission power constraint.
  • the gradient descent method applied to the aforementioned expressions of C j (P) and h(P) when maximizing the generalized mean of the capacities of the transmission channels, may be expressed as follows:
  • the relay device 120 then checks if the resulting matrix P k+1 meets the requirements of the transmission power constraint h(P) . If these requirements are met, the relay device 120 considers that it has found a suitable pre-coding matrix P. Otherwise, another iteration is performed wherein P k+1 becomes P k .
  • P k+1 is projected on the transmission power constraint h(P) as follows, and iterations are performed until convergence of P k+1 and P k+1 :
  • the methods for determining the pre-coding matrix P by using a selection among a plurality of predetermined pre-coding matrices may also be similarly applied in the context of the function representing the capacity of the transmission channel from the source devices 101 , 102, 103, 104 and their respective associated destination devices 1 1 1, 1 12, 1 13, 1 14.
  • the relay device 120 may apply other optimization rules of the transmission channel capacity in order to determine the pre-coding matrix P .
  • the relay device 120 targets determining the pre-coding matrix P that corresponds, taking into account the transmission power constraint h(P) , to a maximum mean value of the transmission channel capacities in the wireless telecommunications network 100, referring to the transmission channels from the source devices 101, 102, 103, 104 to their respective associated destination devices 1 1 1, 1 12, 1 13, 1 14, and for which at least one received flow of complex modulation symbols belongs to the selection obtained in step S301.
  • step S303 the relay device 120 transmits the determined pre- coding matrix P to the destination devices 1 1 1, 1 12, 1 13, 1 14. Then, the step S301 may be repeated to take into account any change of the selection of flows of complex modulation symbols for which the pre-coding has to be applied, and the relay device 120 updates the pre-coding matrix P accordingly.
  • steps S403 and S502 of Figs. 4 and 5 Such a change of the selection of flows of complex modulation symbols for which the pre-coding has to be applied is detailed hereafter with regard to steps S403 and S502 of Figs. 4 and 5 respectively.
  • pre-coded pilots are used in the wireless transmission from the relay device 120 to the destination devices 1 1 1, 1 12, 1 13, 1 14. It is therefore not necessary that the relay device 120 transmit the determined pre-coding matrix P to the destination devices 1 1 1 , 1 12, 1 13, 1 14. In this case, the destination devices 1 1 1 1 , 1 12, 1 13, 1 14 are able to obtain an estimation of the product FjP.
  • the algorithm of Fig. 3 may be periodically executed or be executed when transmission channel conditions change between any source device 101, 102, 103, 104 and the destination devices 1 1 1, 1 12, 1 13, 1 14 and/or between the relay device 120 and the destination devices 1 1 1, 1 12, 1 13, 1 14.
  • the relay device 120 doesn't transmit complex modulation symbols to the destination devices 1 1 1, 1 12, 1 13, 1 14.
  • Fig. 4 schematically represents an algorithm performed by the relay device 120, according to a first embodiment for transmitting pre-coded complex modulation symbols to at least one destination device 1 1 1, 1 12, 1 13, 1 14.
  • the relay device 120 determines information words to be transmitted by at least one source device 101, 102, 103, 104.
  • the relay device 120 receives beforehand these information words from the concerned source device(s) 101, 102, 103, 104.
  • the relay device 120 is further adapted to receive the flows of complex modulation symbols transmitted by the source devices 101, 102, 103 , 104, and makes attempts to retrieve the information words from which the received complex modulation symbols are derived by applying a decoding to the received complex modulation symbols.
  • the relay device 120 is therefore able to use the retrieved information words when the concerned source device 101, 102, 103 or 104 performs a retransmission of these information words.
  • An occurrence of such a retransmission may be determined by capturing and analysing the feedback provided by the destination device 1 10 when an HARQ mechanism is used between the source devices 101, 102, 103, 104 and the destination device 1 10.
  • the relay device 120 determines complex modulation symbols corresponding to, or derived from, the determined information words.
  • the relay device 120 selects at least one flow of complex modulation symbols for which a pre-coding has to be applied.
  • the relay device 120 selects the flow, or flows, of complex modulation symbols for which the relay device 120 succeeded in retrieving, or obtaining, the information word(s) in the step S401.
  • the relay device 120 may in addition take into account information provided by the destination devices 1 1 1, 1 12, 1 13, 1 14.
  • the destination devices 1 1 1, 1 12, 1 13, 1 14 may provide to the relay device 120 information indicating the flow, or flows, of complex modulation symbols for which the concerned destination device succeeded in retrieving the information word(s).
  • this information may indicate the flow, or flows, of complex modulation symbols for which the concerned destination device didn't succeed in retrieving the information word(s).
  • the relay device 120 uses, in addition to the information indicating the flows of complex modulation symbols for which the relay device 120 succeeded in obtaining the information words in the step S401, the information provided by the destination devices 1 1 1, 1 12, 1 13, 1 14, in order to select the flows of complex modulation symbols for which an increasing of the quality is targeted. This allows the relay device 120 to obtain a pre-coding matrix P that focuses the distribution of its transmission power on the signals that are not yet decoded by the destination devices 1 1 1, 1 12, 1 13, 1 14.
  • the relay device 120 applies a pre-coding to the complex modulation symbols determined in the step S402, on the basis of the pre- coding matrix P determined at the step S302. This step enables the relay device 120 to generate pre-coded complex modulation symbols.
  • the steps S403 and S404 may be repeated when a change of the selection of flows of complex modulation symbols for which the pre-coding has to be applied occurs.
  • Such a change may occur during the transmission of complex modulation symbols. Indeed, when two flows of complex modulation symbols are transmitted on the same resource, the transmission of one of these flows may end before the transmission of the other flow. Therefore, a switch from one pre-coding matrix to another may be performed during the transmission of said other flow. This allows optimizing the distribution of the transmission power at the relay device 120 for increasing the quality of signals still under transmission.
  • the relay device 120 transmits to the destination devices 1 1 1 , 1 12, 1 13, 1 14, for which the flows of complex modulation symbols selected in the step S403 are intended, the pre-coded complex modulation symbols obtained during the step S403.
  • the relay device 120 transmits to at least one destination device 1 1 1, 1 12, 1 13, 114 pre-coded complex modulation symbols that allow the increasing of the quality of the signal s received by the concerned destination device(s), and in particular, the increasing of the SINR of these signals.
  • Fig. 5 schematically represents an algorithm performed by the relay device 120, according to a second embodiment for transmitting pre-coded complex modulation symbols to at least one destination device 1 1 1, 1 12, 1 13, 1 14.
  • the relay device 120 takes into account information provided by the destination devices 1 1 1, 1 12, 1 13, 1 14, and which indicates the flow, or flows, of complex modulation symbols for which the concerned destination device succeeded in retrieving the information word(s).
  • this information may indicate the flow, or flows, of complex modulation symbols for which the concerned destination device didn't succeed in retrieving the information word(s).
  • the relay device 120 uses the information provided by the destination devices 1 1 1, 1 12, 1 13, 1 14, for determining the flow of complex modulation symbols for which an increasing of the quality of signals, as received by the concerned destination device, is targeted. This allows the relay device 120 to obtain a pre-coding matrix P that focuses the distribution of its transmission power on the signals that are not yet decoded by the destination devices 1 1 1, 1 12, 1 13, 1 14.
  • the relay device 120 selects accordingly the flows of complex modulation symbols for which the pre-coding has to be applied. For example, on the basis of an information received from the destination devices 1 1 1, 1 12, 1 13, 1 14, the relay device 120 selects a given number of flow of complex modulation symbols for which the signals, as received by the concerned destination devices 1 1 1, 1 12, 1 13, 1 14, exhibit the lowest performance.
  • the relay device 120 obtains estimates of complex modulation symbols to be transmitted in the flow, or flows, selected in the step S502. These estimates may correspond to complex modulation symbols as received by the relay device 120 from source devices, potentially amplified. The relay device 120 then uses these estimates as input to the pre-coding matrix P in order to generate pre-coded complex modulation symbols.
  • the relay device 120 obtains the pre-coding matrix P as described with regard to Fig. 3 and applies the pre-coding to the estimates of complex modulation symbols, on the basis of the obtained pre-coding matrix P. This step enables the relay device 120 to generate the pre-coded complex modulation symbols.
  • the steps S502 and S503 may be repeated when a change of the selection of flows of complex modulation symbols for which a pre-coding has to be applied occurs.
  • the relay device 120 transmits the pre-coded complex modulation symbols obtained during the step S503 to at least one destination device
  • the relay device 120 transmits to at least one destination device 1 1 1, 1 12, 1 13, 114 pre-coded complex modulation symbols that allow the increasing of the quality of the signals received by the concerned destination device(s), and in particular, the increasing of the SINR of these signals.
  • 1 12, 1 13, 1 14 to the relay device 120 may be either directly or indirectly transferred. For instance, such information may be transferred from the destination devices 1 1 1, 1 12, 1 13, 1 14 to the relay device 120 via their respective source devices 101, 102, 103, 104.

Abstract

L'invention concerne un procédé de détermination d'une configuration d'un réseau de télécommunications sans fil visant à augmenter la qualité de signaux reçus par au moins un dispositif destinataire parmi une pluralité de dispositifs destinataires, une pluralité de flux de symboles de modulation complexes étant transmis sur une même ressource par des dispositifs sources respectifs associés à des dispositifs destinataires respectifs, chaque dispositif source transmettant au moins un flux de symboles de modulation complexes sur ladite même ressource au dispositif destinataire qui lui est associé, le procédé consistant à : obtenir un premier ensemble de matrices de canaux représentant des canaux de transmission entre les dispositifs sources et chaque dispositif destinataire et un deuxième ensemble de matrices de canaux représentant des canaux de transmission entre un dispositif relais du réseau de télécommunications sans fil et chaque dispositif destinataire ; sélectionner au moins un flux de symboles de modulation complexes pour lesquels le dispositif relais doit appliquer un pré-codage ; déterminer une matrice de pré-codage destinée à être utilisée par le dispositif relais pour appliquer le pré-codage afin de pouvoir transmettre des symboles de modulation complexes pré-codés sur la même ressource que les symboles de modulation complexes transmis par les dispositifs sources, afin d'augmenter la qualité de signaux reçus par au moins un dispositif destinataire, la matrice de pré-codage étant déterminée sur la base de premier et deuxième ensembles de matrices de canaux, dudit au moins un flux sélectionné de symboles de modulation complexes et d'une contrainte de puissance d'émission s'appliquant au dispositif relais.
PCT/EP2012/051412 2011-02-10 2012-01-30 Procédé d'augmentation de la qualité de signaux reçus par au moins l'un parmi une pluralité de dispositifs destinataires WO2012107306A1 (fr)

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JP2013552901A JP5990199B2 (ja) 2011-02-10 2012-01-30 複数の宛先デバイスの中の少なくとも１つの宛先デバイスによって受信される信号の品質を高めるための方法
US13/983,943 US9225408B2 (en) 2011-02-10 2012-01-30 Method for increasing quality of signals received by at least one destination device among a plurality

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JP5990199B2 (ja) 2016-09-07
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JP2014507094A (ja) 2014-03-20
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